Really interesting answers. I thought there were just a few, but I see there are a lot. The contemporary ones don't surprise me that much, I was more asking about the classic Reshonim and Achronim, but these are great answers nevertheless.
Here's my 2 cents:
Also Nekudos HaKesef on the Taz. While most of it is from the Shach, there are some pieces from his son.
I think if you are splitting up parts, even shticklach, there are many more. Tons of seforim have pieces added by the author's son. I specifically mentioned the word "Chavrusa" in my question.
Sadly, their relationship was totally shattered.
Sounds intriguing. What's the story?
Really interesting. I actually have that sefer (it's an amazing sefer!) and never knew it had dual authorship.